This application is related to and claims priority from Japanese Patent Application No. 2001-7849 filed on Jan. 16, 2001, the content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an air conditioner for a hybrid vehicle having an engine and an electric motor for running the vehicle.
2. Description of Related Art
In a conventional hybrid vehicle having an engine and an electric motor for running the vehicle, a compressor of an air conditioner is driven by the engine, and the engine is automatically stopped in a predetermined vehicle condition such as when the vehicle is stopped and when a vehicle speed is reduced, irrespective of the operation condition of the air conditioner. However, in the hybrid vehicle, even when a vehicle windshield is defrosted, the engine is stopped in the predetermined vehicle condition, and a defrosting function cannot be obtained.
On the contrary, if the engine is continuously operated for obtaining the defrosting function, fuel consumption efficiency is decreased.
In view of the above problems, it is an object of the present invention to provide an air conditioner for a hybrid vehicle having an engine and an electric motor, both for running the vehicle, which improves both of defrosting performance for a windshield and fuel consumption performance.
According to the present invention, an air conditioner for a hybrid vehicle includes a compressor driven by an engine of the vehicle, a cooling heat exchanger for cooling and dehumidifying air to be blown into a passenger compartment by an operation of the compressor, and a control unit for controlling the operation of the compressor. The control unit outputs an air-conditioning preference signal for requiring to drive the engine irrespective of a condition of the vehicle, to an engine controller of the vehicle, in a defrosting control where air cooled and dehumidified by the cooling heat exchanger is blown toward a windshield of the vehicle. Accordingly, in the defrosting control, the engine is driven, and the compressor can be driven by the engine. Therefore, in the defrosting control, defrosting function can be always obtained irrespective of the condition of the vehicle. That is, the engine controller drives the engine irrespective of the condition of the vehicle when the engine controller receives the air-conditioning preference signal from the control unit.
On the other hand, when the defrosting control is not performed, the control of the engine can be performed based on the condition of the vehicle. Therefore, for example, while the vehicle is stopped, the engine is stopped, thereby improving fuel consumption efficiency.
Preferably, the defrosting control is performed when a relative humidity on an inner surface of the windshield becomes equal to or higher than a predetermined value. Therefore, when the relative humidity on the inner surface of the windshield becomes equal to or higher than the predetermined value, the engine is driven irrespective of the condition of the vehicle. Accordingly, the humidity in the passenger compartment can be readily controlled irrespective of the condition of the vehicle.